1. Field of the Invention
The invention relates to digital data transmission systems and more specifically to asynchronous digital data systems including error correction and automatic synchronization circuits for maintaining synchronization when the synchronization code is not detected for several word intervals and for resynchronizing the system where synchronization is lost.
2. Description of the Prior Art
A typical prior art system is disclosed in U.S. Pat. No. 3,805,234, assigned to the same assignee as this patent application. This prior art system includes circuitry for correcting errors, however if synchronization between the sending and receiving circuits is established and then lost due to interference in the communications path for example, synchronization is difficult to re-establish because the receiving circuits cannot recognize the difference between the synchronization code comprising start and stop bits and normal information bits within a data word. These problems are solved by the system which is the subject of this patent application. The system disclosed in this application is a modification and improvement of the system disclosed in U.S. Pat. No. 3,805,234 discussed above.